The excessive presence of phosphorous and nitrogen species in surface and ground water is due, in part, to the application of fertilizers in agriculture, the treatment of municipal wastewater, and the mineral processing industry. High concentrations of nitrogen containing compounds, such as nitrate, nitrite and ammonium, in drinking water can be hazardous to the environment and to human health. For example, nitrate ions can cause cyanosis in children and nitrite ions may cause the appearance of cancers in the digestive system through the formation of nitrosamines or nitrosamides.
Therefore, various techniques, such as biological denitrification, chemical reduction, reverse osmosis, ion exchange, and adsorbtion, have been utilized for the removal of nitrogen ions from water. However, each technique includes its inherent limitations. For example, biological denitrification may not be effective at temperatures below 7° C. and, therefore, may not be useful for treating ground water. Chemical reduction requires the use of various chemicals that may release toxic compounds into the environment, especially when H2 is used as a reductant. Reverse osmosis may not be economical for large water treatment facilities.
Current ion exchange techniques are relatively expensive and retain sulfate and hydrogen carbonate, which induce significant changes in the water composition. In addition, current ion exchange techniques can increase the chloride concentration in water because ion exchange hydrogels replace nitrate with chloride. Adsorption can be used to collect soluble substances from a solution on a suitable interface. For example, adsorption onto activated carbon has been used to treat wastewater. However, activated carbon is relatively expensive, making it uneconomical for large scale water treatment.